1. Field of the Invention
The present invention relates to a light-emitting tube array display device, and more particularly to a light-emitting tube array display device for displaying optional images, in which are arranged in parallel a plurality of light-emitting tubes (also referred to as “display tubes” or “gas discharge tube”) comprising narrow transparent tubes of a diameter of approximately 0.5 to 5 mm having discharge gas filled therein.
2. Description of Related Art
Such a display device as described above is characterized in that high flexibility is provided in the size of a display screen and that a display screen with a curved surface can be realized. In a display device of this kind, electrodes are generally provided outside a light-emitting tube array and a voltage is applied to those electrodes to generate an electric discharge in a discharge gas space inside each light-emitting tube.
The electrodes are disposed outside the tube array by, for instance, printing the electrodes directly on surfaces of the light-emitting tubes by means of a screen-printing method or the like, or by bringing into contact with the light-emitting tubes a supporting plate having the electrodes formed thereon (e.g. see Japanese Unexamined Patent Publication No. 2000-315460).
In a case where the supporting plate is brought into contact with the light-emitting tubes as described above, an adhesive layer is needed at the interface between the electrode and the light-emitting tube so as to obtain good adhesion.
However, in taking out light emitted from the light-emitting tubes as display light, light incident at an angle greater than a critical angle is totally reflected to cause a loss of light in a case where a light-incident substance is higher in refractive index than a light-transmitted substance at a certain interface between two dissimilar substances. Therefore, when a number of interfaces between dissimilar substances exist due to the formation of an adhesive layer and the like, the loss of light is repeated at these interfaces, resulting in a problem that the luminance of a display device is decreased.